For decades if not centuries, firearms have been used for sporting and military purposes. And using firearms for shooting at stationary and moving targets for entertainment or contest purposes has become increasingly popular. Often, firearm training for military purposes is carried out using mock combat situations and arms loaded with blank ammunition. Similarly, some types of contests, e.g., "quick-draw" contests, can be conducted using blank ammunition and electronic timers.
However, using firearms loaded with blank ammunition lacks realism at least because there is no good way to ascertain whether the "shooter" has hit a target.
A rather recent innovation involves firearm-like "guns" which use compressed gas to discharge a projectile such as a small (typically 0.68 inches diameter) paint ball. The ball, being frangible, ruptures upon impact and it is very visibly apparent as to whether and where a "shot" has hit its mark. Earlier uses of such guns involved tree marking in forestry projects and animal marking in conservation or farming projects.
People were quick to realize how such guns could advantageously be used in target shooting and military training involving "war game" or "stalking" contests. And such guns were also quickly adopted for contests not involving military training.
When such pneumatic guns are used in games involving human participants "shooting" at one another, such participants wear protective clothing and face shields. Each participant carries a gun connected to a cylinder of pressurized gas, e.g., carbon dioxide, by a flexible tube. The cylinder is carried on one's back out of the way. The gun has a magazine containing one hundred or more paint balls which are (typically) gravity-fed into discharge position in the gun. Assuming sufficient gas pressure is available and that the gun is functioning properly, a ball is discharged with each squeeze of the trigger.
Pneumatic guns for discharging projectiles such as paint balls are shown in U.S. Pat. Nos. 3,788,298 (Hale); 4,936,282 (Dobbins et al.) and 5,161,516 (Ekstrom). Pneumatic guns for discharging other types of projectiles, e.g., pellets or BBs, are shown in U.S. Pat. Nos. 2,554,116 (Monner); 2,640,476 (Spink) and 3,612,026 (Vadas et al.) and 4,616,622 (Milliman).
While prior art guns of the foregoing types have been generally satisfactory for their intended purpose, some are attended by disadvantages. For example, one such gun uses a single valve to direct pressurized gas from the primary gas chamber to both the projectile and the chamber in which the hammer moves. Gas to the hammer chamber is used to drive the hammer rearward, re-cocking the gun.
Variances in friction between the hammer and its chamber wall, whether caused by wear, dirt or the like, affect the magnitude and duration of hammer pressurization required to fully cock it. If friction is low, the hammer moves quickly and smoothly and the relevant volume of gas in the hammer chamber expands rapidly. Such rapid expansion may detract from the pressure used to discharge the projectile and projectile velocity is reduced.
On the other hand, if friction is higher, the hammer may move more slowly, the volume of gas in the hammer chamber expands slowly and the primary valve is retained open for a longer period of time. As a consequence, substantially full input pressure continues to be applied to the projectile, notwithstanding that it is well down the barrel. This increases projectile velocity.
Either type of event affects the "dynamics" of projectile discharge. Projectile velocity may not be the same from shot to shot. As a result, the gun may require a different aiming point for each shot--this is a very annoying problem for the user.
Another problem relating to pneumatic guns is that of very rapid (but unwanted) cycling or "motorboating," so named because the sound of the gun rapidly cycling resembles that of a motor boat. Such rapid cycling usually occurs when the pressurized gas cylinder is close to being depleted and its pressure low. And it occurs in guns of the type having a single valve simultaneously porting gas to both the projectile and to the hammer chamber. Under circumstances of low gas pressure, the hammer does not re-cock, the gun is unable to discharge a projectile and, sometimes, the bolt fractures a ball which has not yet had time to roll into alignment with the barrel.
When rapid cycling, a gun emits a characteristic, very audible sound. Such sound immediately informs others that the user of such gun is unable to fire and, thus, is more susceptible to "attack."
Yet another disadvantage of certain prior art pneumatic guns is that when a ball-type projectile is fed from a magazine into alignment with the barrel, such projectile may if slightly undersized roll part way down the barrel rather than being retained at the barrel breach. In consequence, a greater volume of gas at a particular pressure is required to discharge the projectile. And because the projectile is "under pressure" for a shorter period of time, it may not attain proper velocity upon discharge.
Yet another disadvantage of certain prior art pneumatic guns is that they cannot be "taken down" or partially disassembled and re-assembled quickly and with minimal or no tools. It is not too uncommon for a paint ball to jam in the gun or for other types of malfunctions to occur. Sometimes such malfunctions result from dirt in the gun or a fractured paint ball. The gun user should be able to quickly disassemble the gun to the degree necessary to clear the cause of the malfunction and, just as quickly, be able to re-assemble it ready to use.
An improved paint ball gun which addresses the foregoing disadvantages would be an important advance in the art.